In Pakistan, army troops are patrolling the streets of the southwestern city of Quetta, where nearly 40 people died and dozens of others were injured in an attack on a Shi'ite Muslim mosque.

Senior Pakistani officials say three unknown assailants entered the mosque in the center of the city as Friday prayers were beginning. They say one of the men blew himself up, while two opened fire at the worshipers. In addition to those killed, the attack left dozens of people injured, and hospital officials say the death toll could go up.

An Interior Ministry spokesman, Brigadier Javed Cheema, says the gunmen were also killed, and authorities are trying to determine their identities. Witnesses are reported as saying they saw two more men outside the mosque who fled the scene.

Pakistani President Pervez Musharraf condemned the attack as a terrorist act, and vowed to punish the culprits.

"It is unfortunate that there are some elements in Pakistan who undermine whatever Pakistan stands for," he said. "I'm very clear in my mind that the vast majority of the people of Pakistan certainly do not contribute to extremism and terrorism and fundamentalism."

The mosque attack brought angry crowds onto the streets in Quetta to condemn the killings. The demonstrators fired shots into the air, and burned vehicles and tires. The violence prompted provincial authorities to declare an indefinite curfew in the city, and army troops are patrolling the streets.

No one has claimed responsibility for what is being described as the deadliest attack against Shi'ites Muslims. Leaders of the minority community are blaming extremists from rival Sunni Muslims who are the majority in Pakistan.

In the central city of Multan, hundreds of Shiite Muslims gathered to mourn the dead. The speakers at the rally accused the government of failing to protect the Shi'ite minority.

The rivalry between Pakistan's radical Sunni and Shi'ite communities has claimed hundreds of lives in recent years.